Electrical interface for heat pump

ABSTRACT

An electrical interface selectively places a heat pump and a backup temperature control device in alternative electrical communication with a single power feed, thereby simplifying installation and reducing cost. In particular embodiments, a compressor of the heat pump may be in selective electrical communication with the power feed via a normally closed relay. Removal of a control voltage results in opening of the normal open relay, and closing of a normally closed relay to place the backup temperature control device in selective electrical communication with the power feed. For a ground source heat pump, a ground loop pump may also be in selective electrical communication with the power feed (e.g., via a normally closed relay).

BACKGROUND

Unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.

Heat pumps are useful for many purposes. A prominent application for a heat pump is as a component for a Heating, Ventilation, and Air Conditioning (HVAC) system used to control ambient temperature within an environment. One example of such an environment is a residential or industrial building space.

Heat pumps are complex mechanisms. They can include refrigerant circulation networks comprising conduits, heat exchangers (e.g., coils), valves, and pumps, as well as other air circulation networks comprising other conduits, heat exchangers, valves, and pumps.

On occasion, a heat pump may experience a failure. Such failed operation of a heat pump can imperil the well being of individuals and/or devices that are relying upon HVAC systems in order to maintain a safe ambient temperature within a space.

SUMMARY

An electrical interface selectively places a heat pump and a backup temperature control device in alternative electrical communication with a single power feed, thereby simplifying installation and reducing cost. In particular embodiments, a compressor of the heat pump may be in selective electrical communication with the power feed via a normally closed relay. Removal of a control voltage results in opening of the normally open relay, and closing of a normally closed relay to place the backup temperature control device in selective electrical communication with the power feed. For a ground source heat pump, a ground loop pump may also be in selective electrical communication with the power feed (e.g., via a normally closed relay).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows a simplified diagram of an example heat pump system according to an embodiment operating in a heating mode.

FIG. 1B shows a simplified diagram of an example heat pump system according to an embodiment operating in a cooling mode.

FIG. 2 shows a simplified view of a line voltage circuit according to an embodiment.

FIG. 3 shows a view of a control voltage circuit according to an embodiment.

FIG. 4 shows a simplified flow diagram of a method according to an embodiment.

DETAILED DESCRIPTION

Described herein are methods and apparatuses implementing an electrical interface with a heat pump. In the following description, for purposes of explanation, numerous examples and specific details are set forth in order to provide a thorough understanding of embodiments according to the present invention. It will be evident, however, to one skilled in the art that embodiments as defined by the claims may include some or all of the features in these examples alone or in combination with other features described below, and may further include modifications and equivalents of the features and concepts described herein.

FIG. 1A shows a simplified diagram of a heat pump system 100 according to an embodiment, in a heating mode of operation. The heat pump system comprises the following elements.

A compressor (COMP) 102 functions to move a working fluid through a circuit 104. The compressor is electrically connected to a power feed 106 via an electrical interface 108 in order to operate.

A working fluid may comprise a refrigerant. A working fluid may experience a phase change as it circulates through the circuit.

A primary side heat exchanger 110 functions to exchange heat with the controlled temperature space 112. The controlled temperature space may be the inside of a building, for example. A fan 113 may operate to assist in the circulation of air within the space.

A secondary side heat exchanger 114 operates to source/sink heat into a thermal reservoir 116 located outside of the temperature controlled space.

The specific (ground) heat pump system of FIG. 1A relies upon the temperature of the ground to serve as a thermal reservoir. A ground loop filled with water is circulated by ground water pump 117. However, embodiments are not limited to this particular configuration.

Some heat pump systems may rely upon the temperature of outside air to serve as a thermal reservoir. Particular heat pump systems could even rely upon a source of geothermal energy, in order to serve as a thermal reservoir.

During the heating mode of operation shown in FIG. 1A, the ground loop is extracting heat from the ground and the heat pump is rejecting this heat into the house. During the process of heating the home, hot gaseous refrigerant from the compressor enters the refrigerant-to-air heat exchanger, and as heat is imparted to the interior space the gas changes phase to a liquid refrigerant. It continues this process until the refrigerant is in a liquid state and is subcooled a few degrees further to condensation of refrigerant vapor.

A metering valve 118 regulates the flow of refrigerant through the circuit. A reversing valve 120 changes a direction of flow of the refrigerant, allowing the circuit to selectively extract or add heat to the temperature controlled space.

FIG. 1B shows a simplified view of the heat pump system of FIG. 1A operating in a cooling mode. In FIG. 1B, heat is being extracted in order to cool the space.

To mitigate risks associated with loss of temperature control in the event of a system failure, as shown in FIGS. 1A-1B, a separate backup temperature control device 130 (e.g., heater, cooler, or heater/cooler) may be supplied together with the heat pump unit. Such a backup temperature control device serves to provide temperature control until the heat pump unit can be repaired.

To operate this backup temperature control device, electrical power is required. Thus, embodiments provide the electrical interface which avoids the need for a second power feed for the backup device. This reduces cost and complexity of the heat pump installation.

In particular, the compressor and the water pump are in communication with a first output 132 of the electrical interface. Under normal operating conditions, power from the power feed is routed to the first output.

The electrical interface also includes a control input 133 and a second output 134. Upon removal of the control input, the electrical interface communicates power from the power feed to the backup temperature control device, rather than to the compressor.

FIG. 2 shows a simplified view of a line voltage circuit 200 according to an embodiment. FIG. 3 shows a view of a control voltage circuit 300 according to an embodiment.

In particular, specific embodiments provide a way of connecting power to multiple elements of the system, by using a set of relays. These relays reliably provide electrical power to the compressor, while offering a robust and mechanical structure of isolating the compressor and providing power to the backup temperature control device in the event of failure.

In the embodiment of FIG. 3 , a control voltage 302 is connected to a relay coil 304 which then mechanically actuates a set of contacts, one being Normally Open (NO) and one being Normally Closed (NC). In such an arrangement, Vcontrol power is alternatively provided to the control coils on contactors CR1 306 and CR2 308.

One example of a candidate relay suitable for use is the Relay Module NO/NC CO Contact available from Peters Indu-Produkt of Germany. This is an example of a singular unit containing NO and NC contacts.

Embodiments could also be implemented in two (2) relays, one NO and one NC powered by the voltage signal. An example is the DPST 1 NO 1 NC 8 Amp Power Relay Module available from CZH-LABS of Shenzhen, China.

The contactors are switched using application of a control voltage to close Normally Open relay 310 and thereby provide power to the compressor (COMP). Normally Closed relay 312 is opened by application of a control voltage 302 and thereby isolates the backup heater from the power feed.

Utilizing an embodiment of an electrical interface as shown in FIG. 3 , power can be applied to one load (e.g., the compressor) or to the other load (e.g., the backup heater/cooler), but not to both electrical loads at the same time. Such a configuration simplifies installation and reduces cost, while still ensuring reliable temperature control over the space.

FIG. 4 shows a simplified flow diagram of a method according to an embodiment. At 402, a heat pump is installed in electrical communication with a power feed.

At 404, the heat pump compressor and pump are selectively electrically isolated from the power feed in response to removal of a control voltage. At 406 a backup temperature control device is selectively placed in electrical communication with the power feed in response to the control voltage removal.

The above description illustrates various embodiments of the present invention along with examples of how aspects of the present invention may be implemented. Other embodiments are possible.

For example, while the above description discloses the backup temperature control device as being a heater, this is not required. Alternative embodiments could feature a backup temperature control device that is a cooler, or a combination heater/cooler.

Moreover, while the above description discloses that removal of a control voltage results in opening of a normally open relay, and closing of a normally closed relay, this is not required. According to alternative embodiments, receipt of a control voltage may result in opening of a normally closed relay, and closing of a normally open relay.

The above examples and embodiments should not be deemed to be the only embodiments, and are presented to illustrate the flexibility and advantages of the present invention as defined by the following claims. Based on the above disclosure and the following claims, other arrangements, embodiments, implementations and equivalents will be evident to those skilled in the art and may be employed without departing from the spirit and scope of the invention as defined by the claims. 

What is claimed is:
 1. An apparatus comprising: a normally open relay between a power feed and a compressor of a heat pump that is in thermal communication with a space; a normally closed relay between the power feed and a backup temperature control device in thermal communication with the space; and a control voltage node configured to receive a voltage signal to open the normally closed relay and to close the normally open relay, thereby isolating the backup temperature control device from electrical communication with the power feed and connecting the compressor to the power feed.
 2. An apparatus as in claim 1 wherein the space comprises a building interior.
 3. An apparatus as in claim 1 wherein the heat pump comprises a ground source heat pump.
 4. An apparatus as in claim 3 wherein the heat pump comprises a geothermal heat pump.
 5. An apparatus as in claim 3 wherein the normally closed relay is further in electrical communication with a ground loop pump.
 6. An apparatus as in claim 1 wherein removal of a control voltage results in opening of the normally open relay, and closing of the normally closed relay.
 7. An apparatus as in claim 1 wherein the normally closed relay is disposed between a power distribution block and the backup temperature control device.
 8. An apparatus as in claim 1 wherein the compressor is in electrical communication with the normally open relay through a first contactor.
 9. An apparatus as in claim 8 wherein the backup temperature control device is in electrical communication with the normally closed relay through a second contactor.
 10. A method comprising: placing a compressor of a heat pump in electrical communication with a power feed through a normally open relay; and in response to a control voltage, closing the normally open relay to connect the compressor to the power feed and isolate a backup temperature control device from electrical communication with the power feed.
 11. A method as in claim 10 wherein: the compressor is placed into electrical communication with the power feed through a normally open relay; and the control voltage causes, closing of the normally open relay, and opening of a normally closed relay between the power feed and the backup temperature device.
 12. A method as in claim 11 wherein the heat pump is in thermal communication with a building space.
 13. A method as in claim 12 wherein: the heat pump is in thermal communication with the space via a fan; and the fan is powered for both cases where the compressor or backup temperature device is used
 14. A method as in claim 12 wherein the backup temperature device is in thermal communication with a building space.
 15. A method as in claim 11 wherein the heat pump comprises a ground source heat pump.
 16. A method as in claim 15 wherein a ground loop pump is in electrical communication with the power feed through the normally open relay.
 17. A method as in claim 11 wherein the normally closed relay is disposed between a power distribution block and the backup temperature control device.
 18. A method comprising: installing a heat pump in electrical communication with a power feed; selectively isolating the heat pump from the power feed in response to a control voltage; and selectively placing a backup temperature device in electrical communication with the power feed in response to the control voltage.
 19. A method as in claim 18 wherein: the heat pump is selectively electrically isolated from the power feed by opening a normally open relay; and the backup temperature device is placed in selective electrical communication with the power feed by closing a normally closed relay.
 20. A method as in claim 18 wherein: the heat pump comprises a ground source heat pump; and a ground loop pump of the heat pump is in selective electrical communication with the power feed through the normally open relay. 